- anaplastic astrocytoma,
- glioblastoma multiforme,
- anaplastic oligodendroglioma.
High-grade gliomas account for approximately 80% of all cerebral gliomas. Prognosis depends on age, grade, performance status, and possibly the extent of remaining disease after surgery. Age is the most important independent prognostic variable at presentation, followed by grade. Performance status is usually recorded using the Karnofsky Performance Scale or the WHO Scale (Zubrod et al. 1960; Karnofsky and Burchenal 1989).
Patients with poor performance status are less likely to be offered treatment. In randomized trials of treated patients with malignant glioma, patients with poor performance status invariably have shorter survival, even accounting for age and grade (Scanlon and Taylor 1979; Walker et al. 1980; Nelson et al. 1985). Site of tumour and volume of tumour on preoperative CT/MRI does not seem to be prognostically important.
Some studies suggest that the amount of peritumoural oedema is associated with a worse prognosis, while others suggest that extensive contrast enhancement, or the volume of tumour remaining on a scan performed at 48–72 hours postoperatively, is associated with poor outcome (Muller et al. 1977; Hammoud et al. 1996; Piepmeier et al. 1996).
Care must be taken when interpreting enhanced images with respect to timing of injection of contrast and the time of performance of the scan. Warnke has demonstrated that tumours can significantly alter in their enhancement on dynamic scanning depending on the delay between contrast injection and performance of imaging.